How to filter differential-mode conducted interference in a PAC (Power Controller Acoustic) system?

The differential-mode conducted interference of the PAC (Power Actuator) is mainly caused by the rectifier circuit of the switching power supply and the transient current of the high-speed digital circuit, with the frequency band concentrated in 150kHz-30MHz.

The filtering scheme adopts a multi-stage differential-mode filter network: at the main power input, an LC filter consisting of a PMH6045 series power inductor (10μH) and X2 safety capacitors (0.1μF/275VAC) is deployed to suppress low-frequency differential-mode noise; at the DC/DC converter output, a second-stage filter is formed by PBZ2012E600Z0T ferrite beads and low ESR solid capacitors to target noise in the 1MHz-30MHz range; for the power supply of sensitive analog circuits, a third-stage RC filter can be added or a PMS series molded inductor can be used; at the same time, the PCB layout should place the filter components as close as possible to the noise source, separate the input and output traces, and reduce parasitic inductance; test verification shows that this filter network can enable the differential-mode conducted interference of the PAC to meet the EN55032 Class A limit in the 150kHz-30MHz frequency band, with an insertion loss of more than 25dB.